In the broadcast audio/video environment, video and audio signals are typically represented in a digital manner, and different transports may be used to move these signals between different equipment. One such transport is Serial Digital Interface (SDI), which is specified by the Society of Motion Pictures and Television Engineers (SMPTE) and the International Telecommunications Union (ITU). This signal transport carries audio and video signals in a serial bit stream between devices over a variety of media, including coaxial cable or fiber optic cable.
The SDI standards can represent a wide variety of video standards, including National Television System Committee (NTSC), Phase Alternating Line (PAL), High Definition (HD) Television (1080i, 720p, 1080p), or Ultra-High Definition (UHD) Television (2160p). Depending upon the video standard being carried, the data rate of an SDI transport may vary among a number of pre-defined rates, ranging from 270 megabits per second (270 Mbps) up to 12 gigabits per second (12 Gbps).
As new standards are defined, the technology to fully implement these standards sometimes trails. In these situations, bridge technologies may be defined. For example, when High Definition Serial Data Interface (HD-SDI) evolved from 1.5 Gbps transport to 3 Gbps transport, a bridge standard was defined that allows a 3 Gbps payload to be carried over two 1.5 Gbps physical links. This is known as a “dual-link”.
Similarly, when 12 Gbps Serial Digital Interface (12G-SDI) Ultra-High Definition standards were defined, a bridge standard was also defined that allows a 12 Gbps payload to be carried over four 3 Gbps physical links. This is known as “quad-link 3G-SDI”.